1. Field of the Invention
This invention is related to an electromagnetic device, and in particular to an electromagnetic device for a camera that can be used as the drive for the shutter, stop, and/or mirror of the camera.
2. Description of Related Art
Small electromagnetic devices are widely used in automatic cameras to drive shutters, stops, and mirrors.
Examples of this type of electromagnetic device for cameras are shown, for example, in Japanese Utility Registration Publication Nos. 64-34621, 61-5766, and 60-18803. Also see U.S. Pat. No. 4,205,287.
In Japanese Utility Registration Publication No. 61-5766, which corresponds to U.S. Pat. No. 4,205,287, an elastic adhesive is provided between a pivot axle and an armature or between the armature and an armature lever. In Japanese Utility Registration Publication No. 60-18803, an elastic adhesive also is provided between an armature and armature lever. None of these references provides an elastic adhesive between a catch located on an armature shaft and an armature lever or places the elastic adhesive in a gap between these two elements. These references also do not include a secondary member for application of a force to the catch.
In Japanese Utility Registration Publication No. 64-34621, a secondary member applies force to a catch. However, no elastic adhesive is used with the secondary member.
FIG. 5 shows this type of electromagnetic device for a camera, which includes a base plate 11. A yoke 13 is situated on the base plate, and includes contact surface 13a.
A coil 15 is wound on the yoke 13. Windings 15a, 15b of coil 15 are connected to a regulating circuit 17. An armature 19 is situated adjacent to yoke 13. A contact surface 19a is provided on armature 19 and is engageable with the contact surface 13a of yoke 13.
A connecting socket 19b is formed in armature 19. One end of an armature shaft 21 is inserted into and connected with socket 19b. A catch 21a is formed on the opposite end of shaft 21.
Between the armature 19 and the catch 21a is situated an armature lever 23. Armature lever 23 includes an opening 23a, which has a diameter larger than the diameter of shaft 21 extending therethrough so that armature lever 23 fits loosely on shaft 21. The armature 19 has force applied to it by a driving spring 25 so that armature 19 is biased in a direction that separates it from the yoke 13.
A socket 2lb is formed in the catch 21a of the armature shaft 21. One end of a reset spring 27 is inserted into socket 2lb. Spring 27 biases armature shaft 21 and armature 19 toward yoke 13 (i.e., spring 27 serves to return armature 19 to the position shown in FIGS. 5 and 6 from the position shown in FIG. 7).
The figure described above shows armature lever 23 and catch 21a at their widest gap. In the condition shown in FIG. 5, the armature 19 is pushed toward the right of the figure by end 27a of reset spring 27, and the contact surface 19a of armature 19 comes into contact with the contact surface 13a of the yoke 13.
In this state, end 25b of the driving spring 25 and end 27b of the reset spring 27 are both pressed down by the reset pin 29 and are not contacting a turned down portion 23b of the armature lever 23; therefore there is no force affecting the armature lever 23. Thus, the armature lever 23 can assume a free position between the catch 21a and the armature 19.
From this state, in which the yoke 13 is magnetized through the regulating circuit 17 so that the armature 19 adheres to the yoke 13, the reset pin 29 is moved in the clockwise direction. The result of this action is that end 25b of the driving spring 25 and end 27b of the reset spring 27 both follow the reset pin 29, rotating in the clockwise direction, and then contact the turned down portion 23b of the armature lever 23. In this way, the armature lever 23 receives the force of the driving spring 25 and of the reset spring 27 and rotates in the clockwise direction around its supporting shaft 31. When it moves the distance of the gap between the catch 21a and the armature 19, the armature lever 23 encounters the catch 21a and the condition shown in FIG. 6 results.
However, with this type of electromagnetic device, which is currently in use, there has been a problem with the contact surface 19a of the armature 19 and the contact surface 13a of the yoke rebounding and separating due to the force of impact when the armature lever 23 contacts the catch 21a, in spite of the existing attractive force generated between yoke 13 and armature 19. The resulting state is shown in FIG. 7.
When the condition shown in FIG. 7 occurs, the arm 23c of the armature lever 23 rotates the pin 33 that drives the shutter, stop, mirror, etc. in the clockwise direction, and if, for example, the pin 33 is the connecting pin for the front shroud or rear shroud, the front shroud or rear shroud will begin its movement, and the camera's components end up moving at times contrary to the camera's prescribed order of movement. This situation has been a drawback to the current electromagnetic devices for cameras.
When the camera's electromagnetic device shown in FIG. 5 is used to regulate the shutter, there is the problem of the reset spring slightly changing its position due to the force of the above-described impact, or due to vibration occurring when end 27b of the reset spring 27 encounters the turned down portion 23b of the armature lever 23, or when the armature lever 23 encounters the catch 21a of the armature shaft 21. Through this change of position, because the direction of the force occurring from the reset spring changes slightly and/or because the reset spring vibrates, there is the problem of the armature lever 23 no longer moving in a stable manner, and the shutter's timing getting thrown off when the yoke 13 is demagnetized by a signal from the regulating circuit 17 in this type of condition.